N.H. Hussin

First Principles LDA+U Calculations for ZnO Materials

The electronic, structural, elastic, and optical properties of zinc oxide (ZnO) with wurtzite-type structure were investigated using first-principles calculation based on density functional theory (DFT) with local density approximation (LDA) plus Hubbard U (DFT–LDA+U)method. Hubbard U improved the calculated results, allowing it to exhibit good agreement with experimental data. The DFT–LDA+U method successfully predicted the electronic properties of ZnO with better described the localization of transition metal Zn 3d electron. The calculated optical dielectric function of ZnO and its relation with electronic properties were further discussed.

First-principles study on structural, electronic and optical properties of TiO2 for dye-sensitized solar cells photoanode

First-principles study based on density functional theory (DFT) framework for structural, electronic and optical properties of titanium dioxide (TiO2) in anatase and rutile phases are investigated. Anatase phase exhibits wide band gap compare to rutile phase. The partial and total density of states for TiO2 (anatase and rutile) describes the occupying of titanium (Ti) and oxygen (O) atoms at each energy level. TiO2 has a high dielectric constant to avoid the recombination process while its high refractive index provides the efficient of light diffusion. The optical absorption of TiO2 occurs in ultraviolet (UV) light of the wavelength photon. The results from the first-principles calculations will be helpful to give an understanding about the properties of TiO2 as promising photoanode in dye-sensitized solar cell (DSSC).

Study of Structural, Electronic and Optical Properties of Lanthanum Doped Perovskite PZT Using Density Functional Theory

Ferroelectric materials of lanthanum (La) doped PbZrTiO3 (PLZT) were investigated via first principles study. The structural, electronic and optical properties of PLZT in tetragonal structure (P4mm space group) were performed in the framework of density functional theory (DFT) with generalized gradient approximation (GGA) and local density approximation (LDA) methods. The calculated results of structural properties of PLZT were seen to be approximately close to the experimental data. The results of the electronic part were covered with the calculation of energy band gap and density of states (DOS). The highest valence band (VB) which lies at the Fermi level (EF) was dominated by the O 2p at F point. The conduction band (CB) of PLZT occurred at G point, which was primarily dominated by Ti 3d mixed at Pb and La p-state. Whereas the optical part was covered with the refractive index and absorption. The refractive index, n and the extinction coefficient, k were calculated with respect to photon energy. Those results obtained could be such a good prediction in studying parameters and properties of new materials.

First Principles Study on Structural and Electronic Properties of PZT and PSnZT Using Density Functional Theory

The geometry optimization of the tetragonal supercell 1x1x2 (P4mm, 99 space group) of PZT and PSnZT were calculated using different exchange correlation functional such as Local Density Approximate (LDA-CAPZ) and Generalized Gradient Approximation (GGA-PBE & GGA-PBEsol).The calculation using functional GGA-PBEsol exhibits the most accurate values of lattice parameter and volume of structure relative to the experiment results with typical error of approximately 1% underestimate (only for PZT-as reference materials). The electronic band structure and density of state (DOS) were also studied in order to understand the electron density and hybrization between cation and anion in the compound. The density of state studies indicated existing of hybridizations among anion O 2p, cation Pb 6s/Sn 5s (special lone pair) and the Ti 3d/Zr 4d states of PZT and PSnZT compound. An indirect band gap was respectively obtained for both cubic PZT and PSnZT at the F-G and Q-G point with 3.154 eV and 2.571 eV.

First principles study on structural and electronic properties of LiFeSO4OH cathode material for lithium ion batteries

Structural and electronic properties of a new fluorine-free cathode material of polyanionichydroxysulfates, LiFeSO4OH with caminite structure are studied using first principles density functional theory. From the calculated result, it reveals that antiferromagnetic configuration is more stable compared to ferromagnetic and non-magnetic configuration. Meanwhile, the density of state calculation divulges that this material exhibited large d-d type of band gap and would behave as a Mott-Hubbard insulator. Thus, this behaviour can lead to poor electronic conductivity.

Structural, Electronic and Optical Properties of Nd-Doped Anatase TiO2 for Dye-Sensitized Solar Cells from Density Functional Theory

The structural, electronic and optical properties of pure and neodymium (Nd) doped anatase titanium dioxide (TiO2)are investigated via first-principles calculations within density functional theory (DFT) approach. The band gap reduces to ~0.398 eV when Ti4+ is substituted with Nd3+ in TiO2 crystal structure. The presence of Nd 4f states in the conduction band of TiO2 clarifies the reducing of the band gap. The dielectric constant and refractive index of Nd-doped TiO2 increase compare to pure TiO2. Nd-doped TiO2 able to enhance light absorption to longer wavelength spectrum. The first-principles results obtained satisfy the criteria for Nd-doped TiO2 to become feasible photoanode material in dye-sensitized solar cell (DSSC) device.

An investigation on the effect of La3+ alteration on structural properties of perovskite PbTiO3: Total energy calculation

In this study, first principles calculations based on density functional theory were used to evaluate optimized sructures and the total energy of the La doped PbTiO3 tetragonal (P4mm phase group). The calculations were conducted using local density approximation (LDA) functional as implemented in Cambridge Serial Total Energy Package (CASTEP) computer code. The different composition of Lanthanum (x) were doped on PbTiO3 resulting Pb1-xLaxTiO3 and its effect on the structural of Pb1-xLaxTiO3 were investigated. The different composition of La changed the lattice parameter and the volume of Pb1-xLaxTiO3. The total energy also were calculated and x= 0.2 is suitable composition of dapant to doped with PbTiO3 which is more stable compared with the other composition. The results are compared with experimental and other theoretical data.

Establishment of Structural and Elastic Properties of Titanate Compounds Based on Pb, Sn and Ge by First-Principles Calculation

Structural, electronic, and optical properties of PbTiO3, SnTiO3, and GeTiO3 tetragonals (P4mm, 99 space group) were investigated using density functional theory as implemented in pseudo-potential plane wave in CASTEP computer code. The calculated equilibrium lattice parameter, electronic band structure, and optical properties for PbTiO3 (reference compound) are in good agreement with the available experiment data. The result also shows that GeTiO3 has a higher tetragonality (c/a=1.18) compared with SnTiO3 (c/a=1.15) and PbTiO3 (c/a=1.05). Calculations of the elastic constants of PbTiO3, SnTiO3, and GeTiO3 tetragonals show that they are mechanically stable. The electronic band structure shows that PbTiO3 has higher indirect band gap at X-G compared with SnTiO3 and GeTiO3, as explained in detail by the optical properties of ATiO3 (A=Pb, Sn, Ge) through the refractive index and absorption coefficient.